1. Field of the Invention
The present invention pertains generally to the field of exhaust systems for internal combustion engines, and is more particularly directed to a system for cooling the exhaust conduits and exhaust gases of an internal combustion engine.
2. State of the Prior Art
Internal combustion engines and particularly Diesel engines are used as power plants or prime movers in environments where highly flammable or explosive materials are handled, such as oil and gas drilling sites and well-heads. An engine operating unprotected in such an environment can present exposed surfaces heated to well in excess of 900 degrees Fahrenheit, creating a fire hazard in the event that flammable material should come into contact with hot engine surfaces. This problem is particularly acute in ocean floor drilling platforms where a limited amount of platform space brings engines into close proximity to the oil and gas conduits. Leaks and spills of greater or lesser magnitude are inevitable and in such a congested operating environment it has been found highly desirable to protect hot engine surfaces against contact with flammable materials. Of particular concern in this respect are the exposed surfaces associated with the engine exhaust, including the exhaust manifold through which flow the gases resulting from fuel combustion in the engine cylinders, since Diesel engine exhaust gases typically range between 800 and 1000 degrees F. A maximum allowable temperature of 200 degrees Centigrade (392 F.) for exposed engine surfaces has been adopted as an industry standard for North Sea installations. Of further concern are spark emissions, particularly from Diesel engines which have a propensity for discharging incandescent particles resulting from incomplete fuel combustion, and the possibility of flash-back of flammable gases entering the hot exhaust conduits, even after the engine has been shut down.
The problems of spark emissions and flashback have been dealt with in the past by means of spark arresters and flame arresters, respectively. Both types of devices are in wide use and are commercially available in a variety of designs.
The problem of cooling the engine surfaces associated with gas exhaust conduits has also been addressed in the past. One exhaust cooling system, which is commercially available and specifically intended to meet the requirements of the oil industry in ocean based platforms, makes use of large water jackets fabricated from sheet metal and bolted over the standard engine exhaust manifolds. A tube provided with its own, separate water jacket carries the hot gases from the manifold into a heat exchanger consisting of a relatively large gas chamber through which extend finned water carrying tubes which absorb heat from the exhaust gases. The gas chamber is itself enclosed in a water jacket in order to maintain its outer surfaces below the maximum permissible temperature. The cooled exhaust gas is then circulated through a flame arrester and a spark arrester and then discharged to the atmosphere. This cooling apparatus is bulky and inordinately heavy, in addition to being unnecessarily complex in that cooling water from the engine cooling system must be directed through three separate water jackets in addition to the cooling tubes in the heat exchanger by means of external tubing provided for this purpose.
This existing cooling system is reasonably effective in protecting hot engine surfaces as well as cooling the exhaust gases, but is unnecessarily complex, heavy and costly, and further improvement thereon is desirable.